Zr-0.8Sn-1Nb-0.3Fe锆合金的微观组织研究

Microstructure of Zr-0.8Sn-1Nb-0.3Fe Zr Alloys

采用光学显微镜和透射电子显微镜对两种制备工艺的Zr-0.8Sn-1Nb-0.3Fe锆合金进行了微观组织分析与表征。实验结果表明增加冷轧次数与退火过程会导致锆合金的晶粒尺寸变大和不均匀化,平均尺寸从3.9μm长大到6.0μm;且析出相的尺寸变大、弥散程度降低,平均尺寸从74.6 nm长大至89.6 nm。增加冷轧次数与退火过程会使基体中的Nb进一步析出,析出相中Nb/Fe比值增加,平均值从1.17增加至1.39。2种锆合金中的析出相主要为面心立方结构的(Zr,Nb)_2Fe化合物,Nb/Fe比值较低,尺寸较大。而在增加冷轧次数与退火过程的锆合金中还观察到少量密排六方结构的Zr(Nb,Fe)_2析出相,Nb/Fe比值较高,尺寸较小。

The microstructure of two types of Zr-0.8Sn-1Nb-0.3Fe alloys prepared with different processes developed by Nuclear Power Institute of China was analyzed using optical microscope and transmission electron microscopy. The results show that with the increasing times of cold rolling and annealing, the crystal grain size of Zr alloy become much larger and less uniform. The average size of crystal grains grows from 3.9 μm to 6.0 μm. Further, the size of precipitates also becomes larger, the dispersion degree becomes less uniform, and the average size of precipitates increases from 74.6 nm to 89.6 nm. Repeated cold rolling and annealing could induce more Nb separating out from the matrix. The average Nb/Fe ratio of precipitates increases from 1.17 to 1.39. Most of precipitates in the two kinds of Zr matrix are（Zr,Nb）2Fe compounds with fcc structure, which have low Nb/Fe ratio and large size. Besides, a few Zr（Nb,Fe）2 precipitates with hcp structure are also observed in the alloy with repeated cold rolling and annealing, but their size is much smaller and the Nb/Fe ratio is larger. Therefore, the cold rolling and annealing process significantly influences the microstructure of Zr alloys.